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GM releases new round of updates for all Bolt EVs

Here we go again…. GM is beginning to notify existing owners of 2018 and 2017 Bolt EVs that they should bring their cars into the dealer for a software update that will improve the way the car behaves in the unlikely case that a battery cell begins to go bad.

The company had previously issued a dealer-installable update for 2017 Bolt EVs and many owners brought their cars in for that update in recent weeks. That update improved the warning to the driver giving them a little more advanced notice before the car was forced to quickly reduce power and then shutdown the propulsion system due to a failing battery cell.

The new update is for both 2018 and all 2017 Bolt EVs even if a 2017 model already had the previous update installed.

For 2017 Bolt EV owners who already had the previous update installed by a dealer, the latest update improves the displayed driving range estimate to take better account of any weak battery cell that may be detected. As an example, some Bolt EV owners with failing cells have reported seeing their estimated driving range suddenly drop from 100 miles to a much lower range.

With the new software, a weak or failing cell detected by the car will result in a more realistic driving range estimate even when the battery pack is fully charged and large sudden drops in predicted range are less likely to occur. The newest update also includes various other drivetrain control improvements that a driver would not normally be directly aware of.

Owners of 2018 Bolt EVs were not notified to receive the previous dealer-installed update because their cars are very unlikely to develop failing battery cells so there was less urgency to apply that update, according to GM spokesman Chris Bonelli. GM decided that 2018 Bolts could wait until the newest update was ready to release.

Aside from these updates, GM continues to use the OnStar communications module in every Bolt EV to periodically check the battery cells in cars in order to detect any developing cell failures before the car shows outward symptoms. GM will notify the vehicle owner if a bad cell is detected and schedule a battery replacement under warranty. The company has said that owners are now very likely to be notified of any developing problem before ever experiencing a reduced propulsion event or unexpected vehicle shutdown.

The exact number of cars that have developed bad cells has not been stated publicly but many cars are believed to come from the first months of early production although some later, mostly 2017 model year cars, have also experienced bad cells. The company says only a “small percentage” of cars will develop a prematurely weakening cell.

GM released the following official statement about the new update:

“General Motors is looking at the entire Bolt EV fleet to ensure everyone has the most updated software available. Through letters we are asking all Bolt EV customers to schedule a service appointment to receive the latest software, including the 2017 owners who received the previously released software calibration. In the event of a cell low voltage condition, this new software increases the accuracy of the range estimation, in addition to providing more warning at low states of charge. We understand this is an inconvenience for some customers to service their vehicles again so soon. However, we want to give our customers the most updated software as soon as it’s available.”

I have seen articles which may leave that impression with some readers as well.

This is a new “recall” or service campaign that covers the same underlying problem but it makes additional fixes that were not part of the earlier update targeted at 2017 Bolt EVs. It has a new “GM Recall” number of 18125 whereas the previous one was 18097. Thus it is confusing to simply frame it has an extension of the earlier fix to new cars (the 2018 cars).

All 2017 Bolt EVs and essentially all 2018 Bolt EVs are recommended to be taken to a dealer that can apply this new update. For 2018 Bolts, it is the first time they are getting the aspects of the fix that were part of 18097 that give the driver more time and notification due to an imminent need to reduce propulsion power and get off of the freeway etc. I’m not sure if any recently built 2018 Bolt EVs have received the new software at the factory already so it’s possible that some 2018 Bolts don’t actually need to be updated. It does seem clear that most or almost all 2018 Bolts need to be updated.

In addition, the 18125 GM Recall update improves the GOM or Guess-O-Meter range estimation behavior so that it better reflects the actual range of the car due to one of the battery cells (cell groups) being less able to hold and release energy due to the cell having a manufacturing defect. Although the GM spokesman I talked to didn’t want to get into the details of the new GOM behavior, I believe what this means is that the GOM now estimates the range based on the weak cell’s voltage and stored energy estimate whereas in the past it was using some kind of averaging across all of the cell groups. Since the weak cell group (with 1 of its 3 cells going bad) is capable of holding less energy it will run out sooner while the other cell groups still have energy. The car must stop withdrawing energy from the battery pack when the weak cell group is empty because continuing to drain it will cause further damage to the cell group and perhaps physically damage it. The 18125 update may also include a small number of other changes or improvements that are not directly noticeable by customers.

With this new GOM update, the car should no longer suddenly show a big drop in estimated driving range when the reduced propulsion warning is given imminently before vehicle powertrain shutdown.

My information comes from a detailed telephone discussion with a GM press representative.